Sketchy Path: Myocardial Response to Ischemia

Question 1

Which vein has the lowest oxygen level in the body?

Answer 1

The coronary sinus

(This is represented by the forge in which one side is glowing and the other side is dark –like how the heart extracts all the oxygen from one side and returns completely empty.)

Question 2

The only way the heart can get more oxygen is through _____________.

Answer 2

dilation of the coronary arteries (like the large dilated red pipe above the oxidative forge with NO written on it)

Question 3

The two main vasodilators in the heart are _______________.

Answer 3

adenosine and NO (like the NO exhaust pipe and the apprentice DaNcINg with the girl with the red, dilated-sleeve dress)

Question 4

Atherosclerotic occlusion limits flow by two mechanisms: _______________.

Answer 4

narrowing of the lumen and decreased NO production (because the endothelium is damaged and can’t make as much NO)

Question 5

Occlusion of the coronaries leads to ischemia in the ____________ compartment first.

Answer 5

subendothelial (like how the less glowing heart is darker on the inside)

Question 6

In addition to decreased supply, ______________ can also cause myocardial ischemia.

Answer 6

increased demand (like the princess demanding that the harp be made faster; she has steam coming out of her ears –to represent HTN – and a steeple-shaped hat –to represent aortic stenosis)

Question 7

The heart has decreased supply during ______-cardia.

Answer 7

tachy

Diastolic time is decreased during tachycardia.

(Think of the queen with the raised heart watch – symbolizing tachycardia –and the falling diastolic diamonds.)

Question 8

Catecholamines can cause coronary artery vasoconstriction through stimulation of the _____________.

Answer 8

alpha-1 receptors

Think of the kid with the cocaine cocoa with the tiny coronary crown.

Question 9

How soon is ischemia symptomatic in heart muscles?

Answer 9

Almost immediately –within seconds

(Think of the ATP batteries falling out of the harp AS SOON AS the king hands it to the blacksmith.)

(Another mnemonic in this Sketch is the floppy strings –it’s meant to represent how the heart stops contracting immediately, also.)

Question 10

Describe the reversible signs of ischemia that can be undone if oxygenation returns in 30 minutes.

Answer 10

• Cell swelling (big belly on repairman)
• Glycogen depletion (eaten candy bar in his pocket)
• Chromatin clumping (tangled string in his other pocket)

(Notice that he’s in front of the sign that says “repaired in 30 minutes or less!”)

Question 11

What are two signs of irreversible cell damage?

Answer 11

• Mitochondrial vacuolization (like the instrument hole in the mitochondria-shaped lute)
• Cell rupture (like the hole in the lute)

(The lute is in a box labeled “Irreparable.”)

Question 12

Two serum markers of irreversible cell injury are _______________.

Answer 12

troponin and CK (like the T-bone steaks and Crispy chicKen spilled in front of the lute)

Question 13

Myocardium that doesn’t immediately return to normal upon reperfusion but does after several days or weeks is referred to as _______________.

Answer 13

stunned myocardium (like the princess who is STUNNED that her harp was repaired so quickly)

Question 14

List the three things that cause reperfusion injury.

Answer 14

• The build-up of intracellular calcium during the ischemic period leads to super contracture of myocytes upon reperfusion (like the guitar that was broken by restringing with the tight red strings).
• The sudden influx of oxygen leads to a burst of metabolism from the pent up demand. This produces superoxides that damage mitochondria (like the mitochondria that caught on fire from the overzealous craftsman).
• The oxide radicals released stimulate inflammatory cells.

Question 15

Ischemic cardiomyopathy is not a true cardiomyopathy (like DCM, hypertrophic cardiomyopathy, or restrictive cardiomyopathy). Describe some of its high points.

Answer 15

• Caused by repeat episodes of ischemia, commonly with old MIs
• Histologic exam shows patchy fibrosis (like the patchy cobwebs on the OLD lute)
• Can lead to systolic heart failure (like the floppy heart balloon above the old lute)

Question 16

Ischemic cardiomyopathy may not be permanent. Explain.

Answer 16

Ischemic myocytes may down regulate their demand and be hibernating (like the hibernating bear). Reperfusion can actually wake up some of the heart (like the red hose aggravating the bear).